As we enter the hurricane season here in south Florida that means afternoon thunderstorms are back. For most people this means little more than inconvenient flash flooding and slower commutes. But for those of us working with sensitive electronics it means something else is back too, dirty power.

When most people hear the phrase “dirty power” they probably think of something like coal, oil, or gasoline. But it has a second meaning as an umbrella term for any sort of electrical abnormality in the voltage, current, or waveform of the electricity being delivered. This can be caused by any number of things from high power devices switching on and off, a noisy electrical meter, or lightning. For most of those reading it will never affect you more than a brief brown out, have your wifi router go nuts, or maybe take out a tv if you're unlucky enough to have a bad surge protector. But if any of you are like me and work with sensitive microcontrollers or bench top power supplies you may have noticed some anomalies in your systems during electrical storms, much like I did the other day.

While working on the control system for the New Boca Bearing Power-wheels, I found my Variable DC  power supply was acting up. It was trying to turn on and even would fire up for a moment before cutting out and trying again. At first I thought it was a problem with my equipment, but after trying my backup Variable power supply and hearing my computer’s battery backup clicking on and off I realized it was a grid issue not an equipment issue. My suspicions were confirmed when I plugged both power supplies into the battery backup and they fired right up without any issue.

The reason plugging into this particular battery backup solved the issue is because it uses special circuitry to tell it when the wall voltage drops below a given threshold, amperage spikes, or it detects a ripple in the AC current. In the event that it detects one of these events it switches to supplying power from the reserves in its batteries until it detects the anomaly has passed. This allows for a steady supply of clean AC voltage to the electronics and helps to stop any unwanted behavior. Normally equipment like this can handle some fluctuation on the input voltage, but there is a limit and thunderstorms are more than capable of finding that limit.

So If you ever find yourself working with equipment that acting funny it may be a case of sensitive equipment acting up because of some dirty electricity and not a completely dead device.